Sochi

A Russian traffic police officer patrols a road near venues at the Olympic Park near Sochi, Jan. 7, 2014.

Russian forces went on combat alert in Sochi and tightened restrictions on access to the Black Sea resort as part of measures by President Vladimir Putin to ensure security at next month's Winter Olympics.

Credit: Kazbek Basayev/Reuters

Volgograd

Russian Cossacks, who started regular patrols within the city in the wake of recent suicide attacks, board a trolley bus while patrolling the streets in the southern Russian city of Volgograd, Jan. 4, 2014.

According to local media, over 400 Cossacks arrived at Sochi on January 9 to provide security for athletes, foreign delegations and tourists.

Cossacks, the descendants of settlers in Southern Russia and Siberia, help maintain law and order in Russian cities by assisting local police in patrols and checking of identification documents and luggage.

Credit: Vasily Fedosenko/Reuters

Sochi

Russian police patrol near accommodation sites and venues in the Olympic Park in Adler near Sochi, Dec. 31, 2013.

Credit: Maxim Shemetov/Reuters

Sochi

Security guards check visitors at the entrance to the Olympic park in Adler, near Sochi, Jan. 16, 2014.

Credit: Alexander Demianchuk/Reuters

Sochi

Police officers patrol on a train at a train station in the Adler district of Sochi, Jan. 17, 2014.

Credit: Alexander Demianchuk/Reuters

Sochi

A Russian Cossack (R) and a police officer (L) stand guard outside a train station as a dog passes by in the Adler district of Sochi, Jan. 17, 2014.

Credit: Alexander Demianchuk/Reuters

Sochi

Police officers stand guard inside a train at the railway station in the Adler district of Sochi, Jan. 17, 2014.

Credit: Alexander Demianchuk/Reuters

Sochi

Military police officers stand guard at a train station in the Adler district of Sochi, Jan. 17, 2014.

Credit: Alexander Demianchuk/Reuters

Sochi

A police officer stands guard at a train station in the Adler district of Sochi, Jan. 18, 2014.

Credit: Alexander Demianchuk/Reuters

Volgograd

Russian Cossacks, who started regular patrols within the city in the wake of recent suicide attacks, check a woman's belongings in front of the Kazan Orthodox Cathedral in the southern Russian city of Volgograd, Jan. 4, 2014.

Credit: Vasily Fedosenko/Reuters

Sochi

Interior Ministry officers check documents of passengers at a railway station of Sochi, the host city for the Sochi 2014 Winter Olympics, April 23, 2013.